System for balancing a tabletop that may be adjustably set in position

ABSTRACT

A torsion spring system for balancing a tiltable tabletop so that it will be retained in any rotative position to which it is set. One or more torsion spring elements are nonrotatively positioned in a rotatable tube carrying two arms for engaging the lower side of the tabletop. Means are provided for locking the torsion spring elements and the rotatable tube into definite rotative positions with respect to each other, and additional means are provided for clamping the tabletop into position after it has been set.

United States Patent Inventor Per G. Bergman Hyggevagen 21, 163 54 Spanga, Sweden Appl. No. 17,052 Filed Mar. 6, 1970 Patented Dec. 7, 1971 Priority Mar. 14, 1969 Sweden 3551/69 SYSTEM FOR BALANCING A TABLETOP THAT MAY BE ADJUSTABLY SET IN POSITION 3 Claims, 12 Drawing Figs.

U.S. Cl 108/2, I 108/6 Int. Cl A471 5/ 12 Field of Search l08/l-l0. 50

[56] References Cited UNITED STATES PATENTS 3,131,654 5/1964 May et al. 108/2 3,140,559 7/1964 Grow et a1. 108/6 3,161,159 12/1964 Kritske 108/2 3,273,517 9/1966 Amthur, Jr. et al. 108/2 Primary ExaminerBobby R, Gay Assistant Examiner-Glenn O. Finch AttorneyBerman, Davidson and Herman ABSTRACT: A torsion spring system for balancing a tiltable tabletop so that it will be retained in any rotative position to which it is set. One or more torsion spring elements are nonrotatively positioned in a rotatable tube carrying two arms for engaging the lower side of the tabletop. Means are provided for locking the torsion spring elements and the rotatable tube into definite rotative positions with respect to each other, and additional means are provided for clamping the tabletop into position after it has been set.

PATENTEDBEB mm 3.625160 ,SHEET 1 OF 3 INVENTOR. PER G. BERG/WAN PATENTEDBEB H911 3.625; 160

SHEET 2 OF 3 av mwm, f

' SYSTEM FOR BALANCING A TABLETOP THAT MAY BE ADJUSTABLY SET IN POSITION BACKGROUND OF THE INVENTION 1. Field of the Invention This invention refers to a system for balancing a tabletop that may be adjustably set in position, and use may particularly be made of the invention in connection with tables having tiltable tabletops or tabletops that may be vertically raised and lowered, respectively, for instance drafting tables and desks.

2. Description of the Prior Art With certain types of tables, for instance tables utilized as drafting tables, it is desirable that the entire tabletop be able to serve as a drafiing board, wherein said tabletop should be able to pivot around a supporting shaft that preferably is positioned parallel to the longitudinal direction of the table and in the proximity of the front edge of the drafting board. Existing tables of this type have had the drawback that with different initial positions of the tabletop it has been necessary to exert different forces for pivoting the tabletop, i.e., when resetting the latter from one position to another.

This invention has the object of eliminating the above-mentioned drawback by providing a torsion spring system efi'ecting balance in each set position of a tabletop, wherein the force necessary to manually pivot the tabletop from one position to another is substantially constant and furthermore very small. The system disclosed by the invention may also to advantage be utilized with tables having tabletops that may be raised and lowered, respectively, in vertical direction, including desks, worktables and Workbenches of various types.

SUMMARY OF THE INVENTION In accordance with the invention, the power for pivoting and raising the tabletop is primarily provided by at least one torsion spring, with the tabletop being provided with locking means so that it may be affixed in a desired raised position.

With tables of the above-mentioned type in which the tabletop serves as a drafting board, the torque of the tabletop or drafting board around the supporting shaft follows a sine curve when the inclination of the drafting board is changed. However, the mathematical curve of the torque of a torsion spring with respect to the angular rotation thereof is a straight line, and this means that it is not possible to introduce a torsion spring directly between the drafting board and the table frame without substantial faults occuring in the balancing. In order that satisfactory balancing be achieved the torsion spring will have to be provided with compensating qualities. In accordance with the invention, the torsion spring is for this reason positioned slightly below the drafting board in the horizontal position of the latter and rearwardly of the supporting shaft of the drafting board, and said spring is connected to one or more, preferably two, lifting arms which actuate the drafting board by means of rollers and cam disks.

One preferred form of the invention is shown by way of example in the accompanying drawings and is described in detail without any attempt to show all of the various forms and modifications in which the invention might be embodied. Hence, the invention should be measured by the appended claims and not by the details of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a perspective view taken from the rear and side of an embodiment of the balancing system of the invention utilized with a drafting table having its tabletop fashioned as a drafting board.

FIGS. 2, 4 and 5, respectively, show side views of the table in accordance with FIG. I with various portions removed,

FIG. 3 shows one end of the frame of the table of FIG. I in a horizontal view with the tabletop removed,

FIG. 6 shows an embodiment of clamping means for the tabletop of the drafting board of FIG. 1, I

FIG. 7 is a cross section of the torsion spring tube, with said cross section being taken at a position for looking a set of torsion springs in the tube,

FIG. 8 shows a component associated with the cross section of FIG. 7,

FIG. 9 is a front view illustrating the torsion spring tube and the component of FIG. 8 in cooperation,

FIGS. 10 and 11 are side views of the balancing system in accordance with the invention applied to a desk, with the tabletop of said desk being in lowered and raised position, respectively, and

FIG. 12 is a front view of the desk in accordance with FIGS. 10 and l 1, respectively.

Identical reference numerals have been utilized in the various figures wherever possible.

DESCRIPTION OF THE PREFERRED EMBODIMENT provided at the front ends of the respective endpieces, with mounting rails 6 for the tabletop 5 that serves as a drawing board being pivotally mounted therein by means of individual pivots 4.

As may be seen more specifically from FIG. 2, a torsion spring or a number of torsion springs in aset 7 of torsion springs are positioned inside a tube 8, which in turn is mounted in a disk 20 that for example may be made of sheet metal, with said tube being locked to the disk 20 by means of a protrusion 21 extending into a corresponding recess 22 in the disk 20. As has been mentioned above, the drafting table has two walls 3a, 3b at each end, and these walls may also consist of sheet metal. The internal end wall 3a is provided with a U- shaped recess 9, which serves as a bearing for torsion spring tube 8, with said tube extending beyond said end wall. This may be seen from FIGS. 3 and 4, which show a horizontal view of the end walls 3a, 3b at one end of the table and a side view of the end wall 3a and the recess arranged therein, respectively, with said recess being provided in a bracket 23 supporting one of the above-mentioned pivots 4 in the illustrated embodiment. The torsion spring 7 positioned inside tube 8 is longer than tube 8 and is anchored in U-shaped recesses 10 in the end walls 3b. This is more specifically shown by FIGS. 3 and 5, respectively, with the last-mentioned figure also showing that recess 10 continues in a bracket 24 affixed to the end wall 311, with said bracket 24 providing a support for pivot 4 in the same fashion as bracket 23. In consequence of the recesses in the respective end walls 3a and 3b being open upwards, the unit consisting of the tube 8 and the torsion spring 7 may very simply be laid in place or lifted out without the assistance of tools.

Each of the disks 20 positioned at the respective ends of the torsion spring tube 8 is provided with an individual lifting arm 11, with said arms being positioned between and above the end walls 30 and 3b. In the illustrated embodiment, the lifting arms 11 are arranged integrally with the disks 20, and the lifting arms 11 are thus detachably mounted on tube 8. Each lifting arm 1 l is provided with a roller 12 at its free end, with said roller rolling on a cam disk 13 when the inclination of the drafting board is changed, said cam disk having a predetermined shape of its cam and being afiixed in the mounting rail 6 on the bottom side of the drafting board.

The torsion spring tube 8 is positioned at a distance of approximately half the length of lifting arm I], counting in horizontal direction, from the fulcrum of the drafting board, i.e., from the pivot 4, which has proved to be appropriate in order for cam disk 13 to have suitable dimensions. If lifting arm II were too short or too long with respect to said distance, cam disk 13 would have such dimensions that the cam disk, lifting arm and roller would not be able to be accommodated between the tabletop 5 and the endpieces 3a, 3b.

The object of the invention, viz, balancing the tabletop to a substantial extent and, in consequence of this, attaining small adjusting forces in repositioning the tabletop between various stable positions of inclination, is achieved as the result of appropriate selection of the location of torsion spring tube 8 with respect to the fulcrum 4 of the drafting board and with respect to the length of lifiing arm 11 as disclosed above.

Torsion spring tube 8 is positioned so low that it does not interfere with the accommodation of the mounting rail 6 and that it does not extend below the lower edge of the top rails 2, which latter makes it possible to hang drawer casings, etc., immediately below the top rails 2.

A device for tensioning and affixing torsion spring 7 in tube 8 is positioned at an appropriate location along tube 8, for instance at its center, and in the illustrated embodiment said device consists of a cylindrical spring-holding disk 14 having a U-shaped recess 25 (compare FIG. 7) into which torsion spring 7 is introduced. The spring-holding disk is affixed by tightening a radially displaceable screw 15 which may slide in a groove 16 in the tube (see FIG. 9) in the transversal direction of the tube when spring-holding disk 14 is rotated (thus when the screw is not tightened), wherein groove 16 preferably covers between 30 and 90 of the circumference of the tube. A shoulder plate 17 is mounted on the outside of tube 8 at one end of groove 16, as may be seen in FIGS. 7 and 9, respectively. An adjusting collar 18 illustrated in FIGS. 7-9 and having its internal radius of curvature equal to the external radius of curvature of tube 8 may be located on the outside of tube 8 and is provided with a groove 19, which for example may be inclined between 15 and 50, preferably approximately 30, with respect to the longitudinal axis of tube 8. Adjusting collar 18 engages shoulder plate 17 when screw 15 is tightened. At the place of engagement between collar 18 and plate 17 the latter may suitably be provided with a rib 17a lying over the corresponding edge of collar 18 and thus preventing the latter from being released from the engagement. Alternatively, the respective edges of plate 17 and collar l8 engaging each other may be tapered in appropriate manner. Counting from outside, screw 15 thus extends in through groove 19, furthermore through groove 16, and into a threaded aperture 26 in spring-holding disk 14. If adjusting collar 18 is slid along tube 8 while concurrently being retained in engagement against plate 17, spring-holding disk 14 will be rotated in consequence of the inclination of groove 19, thereby making it possible to set the torsion spring in a desired position of operation so as to provide the spring or the set of springs with the desired mechanical tension, whereafter said position may be made permanent by tightening screw 15.

If tube 8 is lifted out of the two end walls 3a and 3b, respectively, at one end of said tube it will be possible to introduce or to extract an arbitrary number of individual torsion springs into and out of, respectively, said set of torsion springs, so that a number of spring elements adapted to each individual case of operation may be provided.

FIG. 6 illustrates appropriate clamping means operative on disk 20 in accordance with FIG. 2. FIG. 2 shows that disk 20 is provided with a groove 27 in the form of an arc of a circle. Furthermore, FIG. 4 shows that bracket 23 is provided with a round aperture 23a, and FIG. 5 shows that bracket 24 is provided with a hexagonal aperture 240. The screw 28 illustrated in FIG. 6 and provided with a hexagonal head is axially displaced into the two apertures 23a and 240, respectively, and is locked against rotation by its head 29 being introduced into aperture 240. The following elements are positioned in turn between brackets 24 and 23, viz, a friction washer 320, a disk 20 with its groove 27 in the form of an arc of a circle, through which groove screw 28 extends with a play, furthermore an additional friction washer 32b and a spacer tube 33. A nut 30' is threaded onto screw 28 on the remote side of bracket 23, counting from the head 29 of screw 28, with said nut 30 being provided with a lever 31. Disk 20 may be clamped by fric tional engagement so as to lock lifting arm 11 as the result of nut 30 being tightened by means of lever 31. It may be advantageous to provide spring 7 with a tension such, that the tabletop is automatically set to its uppermost position when the clamping device disclosed above is released, and then it will be an easy matter to set the tabletop to a desired position by depressing the same slightly with ones hand.

FIGS. 10 and 11 are side views of a desk, with FIG. 10 illustrating the top 35 of said desk in its lowermost position and with FIG. 11 illustrating the top 35 in its uppermost position. The desk top 35 is balancedly displaceable in vertical direction as the result of internal legs 36 being able to slide upwards and downwards, respectively, in external legs 37 under the simultaneous actuation of rollers 39 on lifting arms 38 mounted on a tube 40 in manner disclosed by the instant invention, after locking means arranged in appropriate manner have been released. The designation 41 refers to a horizontal floor rail to plus the external legs 37 are fastened. FIG. 12 illustrates the arrangement of FIGS. 10 and 11 as viewed from in front.

As indicated above, the invention is not restricted to the embodiment described above and illustrated in the drawings, and the same may be altered within the scope of the appended claims.

What is claimed is:

l. A system for balancing tabletops in repositioning the latter in a pivotal movement around a first substantially horizontal axis, wherein said system comprises the combination of a frame provided with four legs, two elongate side rails, and a pair of spaced apart internal and external end walls at each end; a unit including an elongate tube having open ends; upwardly open recesses in said internal end walls in alignment with said elongate tube, said tube being rotative in said recesses around a second substantially horizontal axis parallel to said first axis; a pair of parallel lifting arms secured to said tube for engaging the bottom side of said table top; a set of torsion springs comprising a plurality of laminated spring elements disposed in said tube with their ends extending through the respective open ends of said tube; and means for clamping said elongate tube and said set of torsion springs to each other in different rotative positions with respect to each other to vary the torque of said springs; and slots in said external end walls in alignment with said set of torsion springs for receiving the extending ends of said torsion springs, with the torque of said set of torsion springs being also adjustable by varying the number of individual laminated spring elements.

2. A system in accordance with claim I, wherein said means for clamping the set of torsion springs and said elongate tube to each-other in different rotative positions comprises a displaceable collar provided with a groove at an angle of between approximately 15 and 50 to the longitudinal axis of said tube and a retainer plate secured to said tube; said system including a rotative disk in said elongate tube provided with a U-shaped recess for receiving said torsion springs and a setscrew threaded into said disk through said groove in said collar and through a groove passing through said tube at right angles to the longitudinal axis of said tube.

3. A system in accordance with claim 1, wherein said tube is disposed below the tabletop and at a horizontal distance from said first axis equal to substantially half the length of one of the lifting arms and wherein each free end of the two lifting arms engages an individual cam surface on the bottom side of said tabletop.

I! l i 

1. A system for balancing tabletops in repositioning the latter in a pivotal movement around a first substantially horizontal axis, wherein said system comprises the combination of a frame provided with four legs, two elongate side rails, and a pair of spaced apart internal and external end walls at each end; a unit including an elongate tube having open ends; upwardly open recesses in said internal end walls in alignment with said elongate tube, said tube being rotative in said recesses around a second substantially horizontal axis parallel to said first axis; a pair of parallel lifting arms secured to said tube for engaging the bottom side of said table top; a set of torsion springs comprising a plurality of laminated spring elements disposed in said tube with their ends extending through the respective open ends of said tube; and means for clamping said elongate tube and said set of torsion springs to each other in different rotative positions with respect to each other to vary the torque of said springs; and slots in said external end walls in alignment with said set of torsion springs for receiving the extending ends of said torsion springs, with the torque of saId set of torsion springs being also adjustable by varying the number of individual laminated spring elements.
 2. A system in accordance with claim 1, wherein said means for clamping the set of torsion springs and said elongate tube to each other in different rotative positions comprises a displaceable collar provided with a groove at an angle of between approximately 15* and 50* to the longitudinal axis of said tube and a retainer plate secured to said tube; said system including a rotative disk in said elongate tube provided with a U-shaped recess for receiving said torsion springs and a setscrew threaded into said disk through said groove in said collar and through a groove passing through said tube at right angles to the longitudinal axis of said tube.
 3. A system in accordance with claim 1, wherein said tube is disposed below the tabletop and at a horizontal distance from said first axis equal to substantially half the length of one of the lifting arms and wherein each free end of the two lifting arms engages an individual cam surface on the bottom side of said tabletop. 